Polyvinyl acetal silver halide emulsion containing polyvinyl acetal color formers



United States Patent 0 POLYVINYL ACETAL SILVER HALIDE EMULSION CONTAINING POLYVINYL ACETAL COLOR FORMERS M James Harold Taylor, Colonia, and David Willcox Woodward, Fair Haven, N. .L, assignors to E. l. du Pont de Nemours & Company, Wilmington, Del., 2 corporation of Delaware No Drawing. Application June 23, 1953 Serial No. 363,654

13 Claims. (CI. 96-74) This invention pertains to photography and more particularly to a process of preparing color former silver halide dispersions and photographic elements bearing photographic layers of such dispersions. Still more particularly, it pertains to such processes wherein the colloid binding agents for the silver halide grains comprise benzaldehyde polyvinyl acetals.

In the preparation of multilayer color films utilizing synthetic colloid binding agents for the silver halides, it

has been the custom to separately prepare each silver halide emulsion for each respective photographic silver halide emulsion layer. This is inconvenient because it involves a duplication of steps. Thus, a separate operation of grain precipitation and growth, coagulation, washing and redispersion for each of the three emulsions 1 layers wherein the light-sensitive silver halide grains exhibit similar size distribution in each layer. A further object is to provide a more rapid and eflicient manner of preparing the plurality (generally three) of polyvinyl acetal color forming silver halide emulsions or dispersions for coating multilayer color films. Still other objects will be apparent from the following disclosure.

It has been discovered that benzaldehyde polyvinyl acetals are excellent protective colloids for silver halide grains and that the aqueous silver halide dispersions made with such colloid binding agents can be ripened to the desired grain size distribution, split into portions and each portion mixed with a polyvinyl acetal color-former, and, if desired, other water-soluble, non-color-forming colloids such as polyvinyl alcohol, partially hydrolyzed polyvinyl acetate, polyvinyl acetals, etc. Two or more of'such portions can be mixed with a spectral sensitizing dye or dyes and other emulsion adjuvants to produce aqueous coating compositions suitable for coating as cooperative layers onfilm base or paper, and the silver halide grain size distribution and history of treatment of the resulting layers will be eessentially the same, thus providing good sensitometric balance in the multilayer photographic element.

The novel process of the invention in its broader aspects comprises precipitating light-sensitive silver. halides in an aqueous solution of a benzaldehyde polyvinyl acetal, allowing the silver halide grains to grow (ripen) to the desired extent, removing the water-soluble salts, if desired, dividing the resulting aqueous dispersion into portions, admixing with respective separated portions a dif-v ferent polyvinyl acetal color-former capable of yielding an azomethine or quinoneimine dye upon color coupling development of the exposed silver halide grains, and adice 1 2 mixing with at least two of such portions an appropriate spectral sensitizing dye; so that the resulting emulsions have strong sensitivity in different primary color regions of the spectrum. The resulting dispersions are admixed with additional benzaldehyde polyvinyl acetal or other emulsion adjuvants, as desired, such as non-color-forming, water-soluble colloids to control the emulsion water-sensitivity, swelling, viscosity, film' thickness, coating weight, etc. For example, the layers may contain from to 50% by weight of a water-soluble or hydrophilic polyvinyl alcohol or a partially hydrolyzed polyvinyl ester or a polyvinyl acetal, e. g., the sodium o-sulfobenzaldehyde acetal of polyvinyl alcohol and benzaldehyde acetal of polyvinyl alcohol. They are then coated as superimposed layers on a suitable sheet support such as a film base or paper base. A blue light absorbing medium is provided either as a yellow dye or pigment in the blue-sensitive layer or as a separate filter layer to prevent blue light from exposing any spectrally sensitized layer.

In a preferred aspect of the invention, a mixture of light-sensitive silver halides is precipitated in an aqueous ethanol solution of a benzaldehyde polyvinyl acetal colloid, the silver halide grains permitted to ripen, the dispersion of the silver halides in said acetal coagulated, the coagulated dispersion Washed free from dissolved inorganic salts, the washed coagulate redissolved in aqueous ethanol and admixed, if desired, with more of said acetal, or other non-color-forming colloid and the resulting solution divided into portions, each portion admixed with an aqueous ethanol solution of a difierent polyvinyl acetal color former capable of yielding a quinoneimine or ammethine dye upon color-coupling development of exposed silver halide grains, and admixing with two or more of such portions and appropriate spectral sensitizing dye and other emulsion adjuvants respectively, so that the resulting emulsions have strong sensitivity in diiierent primary color regions of the spectrum. The resulting dispersions are then coated as superposed layers on a suitable sheet support such as a film base or paper base.

The benzaldehyde polyvinyl acetals useful in accordance with the invention are hydrophilic colloids which contain a large number of intralinear vinyl alcohol units to give them hydrophilic properties. They may also contain a substantial proportion of other acetal groups from aliphatic or aromatic aldehydes containing carboxylic and/ or sulfonic acid groups or their watersoluble salts to increase the water-solubility and/ or water permeability of the acetals. The latter aldehydes are, of course, devoid of groups which form color during the color development reaction between silver halide and pphenylenediamine type color developers. This means that the mixed acetals with benzaldehyde linkages and the simple benzaldehyde polyvinyl acetals are non-color-forming polyvinyl acetals.

The polyvinyl acetals described in the next preceding paragraph can be prepared by any conventional acetalization reaction from the stated aldehydes or their ethylene glycol or dimethyl or diethyl acetals and an acid' catalyst, preferably in an ethylene glycol medium. Suitable procedures are described in Dorough and McQueen U. S. Patent 2,310,943, Martin U. S. Patent 2,513,189, and German Patent 643,650. They can be made from polyvinyl alcohol or partially hydrolyzed polyvinyl esters and hydrolyzed olefine/ vinyl acetate copolymers and may contain small amounts of other non-color-coupling groups as shown in said U. S. patents.

The polyvinyl acetal colpr formers which can be blended with the benzaldehyde polyvinyl acetals are essentially colorless, synthetic polymers which have protective colloid properties and form water-permeable layers. They con- CHLOE-CHz-CH where X is a color-former group or nucleus and Y is a solubilizing group enhancing hydrophilic character, and the letters a, b and c represent the proportions of such groups and are selected to contribute the desired colloid properties and to provide the required color density after color-coupling development.

In the polyvinyl acetal color'formers, the color-former nuclei need not be directly attached to the CH groups but may be part of a radical or group which is so attached. The color-former nuclei have as the active group a structure which may be represented by the formula: X =H wherein X isHO- or, RHN-, wherein R is hydrogen or an aliphatic group and n is' or 1. The free or dangling valences may, of course, be satisfied by various atoms or groups, e. g., hydrogen, halogen, carboxylic or sulfonic acid groups andtheir derivatives, fused rings, alkyl, aryl, alkoxy, aryloxy, etc. The hydrogen atom in the formula may be replaced by groups readily displaced in the coupling reaction, e. g., halogen atoms, carboxylic or sulfonic acid groups; This active group is found in the active methylene color formers or dye intermediates and in aromatic hydroxyl and amino compounds and include the reactive ethenol,'aminoethenyl, 4-hydroxyand 4-amino- 1,3-butadieny1 groups. These groups occur in phenols, naphthols, aromatic amines, acylacetamides, beta-ketcesters', pyrazolon'es, homophthalimides, cyanoacetyl compounds, etc. The reactive ethenol group as represented y and others. The -CH group is usually present between two such groups, e. g.,

, -COCHz,CO.--. -cooH,cN, COCH1( )=N in a cyclic or acyclic system. The enol forms of these examples are and . 4- The reactive aminoethenyl group RHNC=CH occurs in aromatic amino compounds which couple in the ortho position.

The 4-hydroxyand 4-amino-1,3-butadienyl groups represented as RHN-( 3=b--d=cH-- occur in phenolic, naphtholic and aromatic amino compounds which couple in the para position.

Among the specific polyvinyl acetal color formers which can be used in accordance with the invention are those described in the following U. S. Patents: 2,310,943, 2,320,422, 2,380,032, 2,380,033, 2,397,864, 2,397,865, 2,415,381, 2,422,680, 2,423,572, 2,464,597, 2,465,067, 2,472,666, 2,472,910, 2,472,911, 2,472,913, 2,473,403, 2,476,988, 2,477,462, 72,513,189, 2,513,190, 2,538,257, 2,562,527, 2,562,528, 2,575,182, and in U. S. applications Martin Ser. No. 172,191, filedJuly 5,, 1950, now U. S. Patent 2,680,730 and Martin Ser. No. 172,192, led July 5, 1950, now U. S. Patent 2,680,731. These hydroxyl polymer color formers or vinyl alcohol polymers may contain a substantial proportion of sodium o-sulfobenzaldehyde acetal or equivalent groups as taught in said patents. In general, the linear unit CH -CHOH should represent at least 50% of the polymer chain, between 1 and 35 color-former nuclei should be present for each chain atoms and the polymer chain be in excess of 200 carbon atoms. Of course, minor amounts of lower molecular weight polymers may be present.

The invention will be further illustrated but is not intended to be limited by the following examples in which the preparation, coating, etc., of the photographic elements is carried out in the substantial absence of radiation which would produce exposure of the materials in process. The polyvinyl alcohol used in :these examples is, unless otherwise stated, medium viscositycompletely hydrolyzed (viscosity of 4% aqueous solutionat 20 C., 15 to 20 centipoises).

Example I V V i A One and one-half (1.5) mols of silver bromide are precipitated in an aqueous ethanol'solution containing as a protective colloid 40 grams of an acetal made by reacting on a weight basis 100 parts of polyvinyl alcohol with 10 parts of benzaldehyde and 2 parts of benzaldehyde 0- sodium sulfonate. After the completion of a 75 minute ripening period at F., the silver halide polymer dispersion is coagulated, washed with water to remove soluble salts and redispersed in a solution of 28% ethanol by weight in water, and the pH adjusted between the limits 8.9 to 9.1, after which an additional 40 grams of the same mixed polyvinyl acetal is added. This re dispersed emulsion is divided into three parts in preparation for coating. One part. is admixed with tartrazine ;(C. I. No. 640) and 324 grams per mole of silver of a yellow color-forming polyvinylacetal made by reacting on a weight basis 100 parts polyvinyl alcohol, 17 parts mbenzoylacetamidobenzaldehyde ethylene glycol acetal, and 08 part benzaldehyde o-sodium sulfonate'as described in U. S. Patent 2,513,190; another part is admixed with 254 grams per mol ofsilver of a cyan color-forming polyvinyl acetal made by reacting on a weight basis 100 parts polyvinyl alcohol, 20 parts m-(3-methylsalicylamido)-benzaldehyde ethylene glycol acetal and 1.5 parts benzaldehyde o-sodium sulfonate as described in U. S. Patent 2,489,655; while the third part is' admixed with 324 grams per mol of silver of a magenta color-forming polyvinyl acetal made by reactingon a weight basis 100 parts polyvinyl alcohol, 18 parts 2-cyanoacetyl'-3 phenyl- S-benzofuraldehyde ethylene glycol acetal, and 1 part benzaldehyde o-sodium sulfonate as described in Martin U. S. patent application Ser. No. 193,297, filed October 31, 1950, now U. S. Patent 2,680,732. 'The three emulsions are modified by the addition of a sulfur sensitizer; the emulsion containing magenta color former is sensitized to green light by the addition of a symmetrical oxycarbocyanine dye and the emulsion containing cyan color-forming polymer is sensitized to red light by an unsymmetrical thiocarbocyanine dye which confers no sensitivity in the green region of the spectrum, and the three emulsions are then separately digested and prepared for coating.

A multilayer negative film is then made by coating the three emulsions on 0.005 inch thick cellulose triacetate film base to which have been applied, in order, two thin nitrocellulose layers and an emulsion substratum layer (containing a yellow color-forming polymer of the foregoing type) on one surface and on the other surface a sublayer and a non-halation layer. The green-sensitized, magenta color-forming emulsion is coated directly on the substratum to a silver halide coating weight of 35 mg.

per sq. dm. On the emulsion layer is coated a thin separator layer (12 mg. per sq. dm.) of polyvinyl alcohol on which is coated the red-sensitized cyan color-forming emulsion to a silver halide coating weight of 37 mg. per sq. dm. Next there is applied another thin polyvinyl alcohol separator layer over which is coated the bluesensitive yellow color-forming emulsion so as to give a silver halide coating weight of 35 mg. per sq. dm. The resulting film was evaluated by preparing a series of step-wedge exposures through appropriate filters on a laboratory sensitometer (non-intermittent intensity scale sensitometer employing a neutral density wedge for modu-' lation of printing light). The exposed films were processed to color images as described in the Journal of the Society of Motion Picture and Television Engineers, November 1950, pp. 455-476. The sensitometric strips so obtained Were read on a precision integrating-sphere densitometer (J. G. Frayne, with G. R. Crane), Journal of the Society of Motion Picture Engineers, volume 35, No. 2, August 1940, p. 184), and a modification of this densitometer (A. C. Lapsley and J. P. Weiss, Journal of the Society of Motion Picture and Television Engineers, vol. 56, January 1951, p. 23). The evaluation demonstrated that the complete multilayer film had satisfactory speed, gamma and color balance for use in a motion picture color duplicating negative.

Example II One and one-half (1.5) mole of silver bromide are precipitated under conditions known to give a high contrast emulsion in an aqueous ethanol solution containing as a protective colloid 40 grams of an acetal made by reacting on a weight basis 100 parts of polyvinyl alcohol, 10 parts benzaldehyde and 2 parts sodium benzaldehyde o-sulfonate. After the completion of a ripening period designed to give maximum contrast, the silver halide polymer dispersion is coagulated, Washed with water to remove soluble salts and redispersed in a solution of 28% ethanol by weight in water and the pH adjusted between the limits 8.9 to 9.1 after which an additional 40 grams of the same mixed polyvinyl acetal is added. This re dispersed emulsion is divided into three parts in preparation for coating. One part is admixed with 460 grams per mol of silver of a yellow color-forming polyvinyl acetal made by reacting on a weight basis 100 parts polyvinyl alcohol, 61.5 parts rn-benzoylacetamidobenzaldehyde ethylene glycol acetal and 29 parts benzaldehyde o.-sodiurn sulfonate as described in U. S. Patent 2,513,190; another part is admixed with 564 grams per mol of silver of a cyan color-forming polyvinyl acetal made by reacting on a weight basis 100 parts polyvinyl alcohol, 20 parts m-(3-methylsalicylarnido)benzaldehyde ethylene glycol acetal and 1.5 parts sodium benzaldehyde o-sulfonate'as described in U. S. Patent 2,489,655; while the third part is admixed with tartrazine (C. I. No. 640) and 5 64 grams per mol of silver of a magenta color-forming polyvinyl acetal made by reacting on a weight basis parts polyvinyl alcohol, 18 parts 2-cyanoacetyl-3-phenyl- S-benzofuraldehyde ethylene glycol acetal, and 1 part sodium benzaldehyde o-sulfonate as described in Martin U. S. patent application Ser. No. 193,297, filed October 31, 1950, now U. S. Patent 2,680,732. The three emulsions are modified by the addition of a sulfur sensitizer; the emulsion containing yellow color former is sensitized to green light by the addition of a symmetrical oxycarbocyanine dye and the emulsion containing cyan colorforming polymer is sensitized to red light by an unsymmetrical thiocarbocyanine dye which confers no sensitivity in the green region of the spectrum, and the three emulsions are then separately digested and prepared for coating.

A multilayer positive film is then made by coating the three emulsions on 0.005 inch thick cellulose triacetate base to which have been applied, in order, two thin nitrocellulose layers and an emulsion substratum layer (containing a yellow color-forming polymer of the foregoing type) on one surface and on the other surface a.

sublayer and a non-halation layer. The green-sensitized, yellow color-forming emulsion is coated directly on the substratum to a silver halide coating weight of 55 mg. per sq. dm. On this emulsion layer is coated a thin separator layer (12 mg. per sq. dm.) of polyvinyl alcohol on which is coated the red-sensitized cyan colorforming emulsion to a silver halide coating weight of 28 mg. per sq. dm. Next there is applied another thin polyvinyl alcohol filter layer containing yellow colloidal silver (to augment the filtering of blue light by the tartrazine dye) and on this layer is coated the blue-sensitized magenta color-forming emulsion so as to give a silver halide coating weight of 22 mg. per sq. dm. When this film is exposcdto appropriately colored light through black and white component ngeatives comprising the blue, green and red records of a multicolor scene and processed to a color-positive as described in the Journal of the Society of Motion Picture and Television Engineers, November 1950, pp. 455-476, a color positive of excellent color quality is obtained. Alternatively, the film may be exposed to a color negative resulting from the appropriate exposure and processing of a film of the type described in Example I. When processed as described above a color print of excellent quality can be obtained.

Example III A multilayer color film was prepared as described in Example I except that the protective colloid for the precipitation of the silver bromide was prepared by reacting on a weight basis 100 parts of polyvinyl alcohol, 10 parts of benzaldehyde and 3 parts of benzaldehyde o-sodium sulfonate. The resulting film was evaluated as described in Example I with similar results.

Example IV A redispersed emulsion was prepared as described in Example I except that the protective colloid for the precipitation and redispersion of the silver bromide was prepared by reacting on a weight basis 100 parts of polyvinyl alcohol, 6 parts of benzaldehyde and 1.25 parts of benzaldehyde o-sodium sulfonate. The resulting emulsion was divided in two parts and the one portion mixed with 243 grams per mol of silver of the cyan color-forming acetal described in Example I. The remaining portion was mixed with 324 grams per mol of silver of the yellow color-forming acetal described in Example I, the emulsions were sensitized, coated on separate films and evaluated using the procedure described in Example I. This evaluation demonstrated that the individual colorforming emulsions had satisfactory speed and gamma and grain size distribution for use in a color duplicating negative filmof the type described in Example I.

Example V A redispersed emulsion was prepared. as, described inv Example I except that the protective colloid for the precipitation and redispersion of the v silver bromide, wasv prepared by reacting on a weight basis 100' partsaof polyvinyl alcohol, 13 parts of benzaldehyde and. 7] parts ofbenzaldehyde o-sodium sulfonate. The resulting emulsion was mixed with, 267 parts per mol of silver, of a yellow color-forming acetal made by reacting on a weight basis 100, parts of polyvinyl alcohol, 61.5 parts of rn-.

benzoylacetamidobenzaldehyde ethylene glycol acetal and 29 parts of benzaldehyde. o-sodium sulfonate, sensitized, coatedonfilm andtested, as described in Example I. The emulsion, was found, to have satisfactory speed, gamma and grain size distribution for use in a color duplicating negative film of the type describedin that example.

Example VI- A redispersed emulsion was prepared as described in Example I except that the protective colloid for the precipitation and redispersion of the silverbromide was prepared by reacting on a weight basis 100" parts of polyvinyl alcohol, 13 parts of benzaldehyde and 4' parts of benzaldehyde o-sodium sulfonate. The resulting emulsion was used in preparing a cyan color-forming emul- Example V11 A redispersed emulsion is prepared as in Example I, using ripening conditions adjusted to give high contrast silver bromide. This redispersed emulsion is divided into three parts. One part is mixed with 200 grams per mol of silver of a yellow color-forming polyvinyl acetal made by reacting on a weight basis- 100 parts of polyvinyl alcohol, 61.5 parts m-benzoylacetamido-benzaldehyde ethylene glycol acetal and 29 parts of sodium benzaldehyde o-sulfonate as described in U; S. Patent 2,513,190, and 200 grams of polyvinyl alcohol; another part is admixed with 175 grams per mol of silver of a cyan color-forming polyvinyl acetal made by reacting on a weight basis 100 parts polyvinyl alcohol, 60 parts m- (B-methylsalicylamido)benzaldehyde ethylene glycol aceta1, and, 30-parts sodium benzaldehyde o-sulfonate as d e-- scribed in U. S. Patent 2,489,655, and 200 parts of polyvinyl alcohol, while the third part is admixed with 200 grams per mol of silver of a magenta color-forming polyvinyl acetal made by reacting on a weight basis 100 parts of polyvinyl alcohol, 60 parts of 2-cyanoacetal-3-phenyle S-benzofuraldehyde ethylene glycol acetal and 20 parts sodium benzaldehyde o-sulfonate as described in U. S. application Ser. No. 193,297, filed'October 31, 1950, now U. S. Patent 2,680,732 and 2 00 partsyof polyvinyl alcohol. The three emulsions are modified by the addition of a sulfur sensitizer. The, emulsion containing the magenta color-former is sensitized to green by the addition of a symmetrical oxycarbocyanine dye and the emulsion containing cyan color-formingpolymer is, sensitized; to. red light by an unsymmetrical thiocarbocyanine dye which confers no sensitivity in the green region of the. spectrum and the three emulsions are then; separately digested and prepared for coating. A multilayer negative film is prepared by coating on a base; such as is described in Example I the red sensitized cyan color-form; ing emulsion. Onto this emulsion layer is coated the green-sensitized magenta color-forming emulsion and there is next applied a layer of colloidal silver. having. an optical density to blue light of 1.5 over which, is coated the blue-sensitive yellow: color-forming emulsion, The.

completed film is exposed to light from a color negative: having the same conventional layer arrangement of color-formento emulsion-sensitivity and processed as describedin Example-ll to a color-positive ofexcellent color quality.

The silver halides can be precipitated inthe foregoing emulsions in the usual manner by dissolving asoluble, ionizable halide, e. g., sodium, potassium, or ammonium chloride, bromide or iodide, ormixtures thereof in water, and byv dissolving separately in water a soluble, ionizable silver salt, e. g., silver nitrate, silver sulphamate, silver acetate or silver citrate ormixtures oftwo or more such compounds. The two solutionsare admixed with the solution. of the simple or mixed benzaldehyde polyvinyl acetal. in anyorder and in one or several portions 'depending on the particular photographic qualities desired.

After redispersion of the coagulatedsilver halidedispersions in the benzaldehyde polyvinyl acetals the emulsions can be modified before orafter addition with the color-forming polyvinyl acetal by the addition of general emulsion sensitizers, e. g-., allyl thiourea, phenyl isothiocyanate, sodium thiosulfate, and allyl isothiocyanate, antifogging agents, e. g., 2-mercaptobenzothiazole; 1- phenyl-S-mercaptotetrazole, benzotriazole, and S-nitrobenzimidazole; sensitizing dyes, hardeners, e. g., formaldehyde and other aliphatic aldehydes, dimethylol urea, trimethylol melamine, chrome alum and other chromium compounds or other emulsion adjuvants.

Other water or water-alcohol soluble non-color-forming colloids suchas polyvinyl, alcohol, partially hydrolyzed; polyvinyl acetate, partially orcompletely hydrolyzedcopolymers of vinyl acetate or acetals of these with aldehydes free of groups which form colored products in the color development reaction, esters or ethers of cellulose or starch, polymers-orcopolymers of acrylic or methacrylic acid; etc., can be addedas desired to improve the solution viscosity, increase the film thickness or improve film permeability. In addition to the solubilizing aldehydes of the examples, other aldehydes containing ionic groups can be used in the polymer, such as o.-phthalaldehydic acid, sodium benzaldehyde-m-sulfonate, p-carboxyphenyl-benzaldehyde, glyoxylic acid, succinaldehydic acid, adipaldehydic acid; or 3-formylcyclohexaneoic acid can. be used. Also, minor amounts of acetal groups prepared from p-hydroxybenzaldehyde, formaldehyde, acetaldehyde, furaldehyde, butyraldehyde, etc., can be included in the polymers as desired to modify the solubility and permeability characteristics.

An advantage of this invention is, that it provides, a

simple and practical method of preparingv a plurality of silver halide polyvinyl acetal color-forming emulsions. Another advantage resides in the fact, that the benzaldehyde polyvinyl acetals give lower fog values than related acetals. A further advantage is that multilayer papers and films coated from the emulsions have uniform grain size distribution. 7 V fact that the multilayer films and papers made from the emulsions have good sensitometric balance. A still further advantage accrues from the economies. of operation resulting from the use of continuous emulsion manufacture techniques.

What is claimed is:

l. A process which comprises precipitating light-sensitive silver halides in an aqueous solution of a non-colorforming polyvinyl acetal: taken from the group consisting ofsimple polyvinyl acetals of polyvinyl alcohol with benzaldehyde and mixed acetals of" polyvinyl alcohol with benzaldehyde and an aldehyde taken from the class consistingof aliphatic and aromatic carboxylic and sulfonic acids and their water-soluble salts, carboxylic and sul fonic groups being the sole substitueut groups attached to the hydrocarbon nucleusyof said aldehydes, said polyvinyl acetals containing a large number of recurring intralinear,CH -CI-IOH- groups and being'hydrophilic character, allowing the silver halide crystals to ripen and A further advantage resides in the.

where X is taken from the group consisting of primary amino, secondary amino and OH groups and n is a number taken from the group consisting of and 1.

2. A' process which comprises precipitating light-sensitive silver halides in an aqueous solution of a hydrophilic macromolecular mixed acetal of polyvinyl alcohol with benzaldehyde and an aldehyde containing a solubilizing group taken from the class consisting of carboxylic and sulfonic acids andtheir water-soluble salts, the carboxylic and sulfonic groups being sole substituent groups attached to the hydrocarbon nucleus of said aldehyde, said polyvinyl acetals containing a large number of recurring intralinear -CH CHOH- groups, allowing the silver halide crystals to ripen and admixing with the dispersion a water-permeable colloid at least a part of which is a polyvinyl acetal color former capable of forming upon color coupling development of an exposed silver salt image a dye taken from the group consisting of quinoneimine and azomethine dyes and containing in one of its tautomeric forms as an integral part of the molecule an active coupling group of the structure tive silver halides in an aqueous solution of a non-color-v forming polyvinyl acetal taken from the group consisting of simple polyvinyl acetals of polyvinyl alcohol with benzaldehyde and mixed acetals of polyvinyl alcohol with benzaldehyde and an aldehyde taken from the class consisting of aliphatic and aromatic carboxylic and sulfonic acids and their water-soluble salts, the carboxylic and sulfonic groups being the sole substituent groups attached to the hydrocarbon nucleus of said aldehydes, said polyvinyl acetals containing a large number of recurring intralinear CH CHOH groups and being hydrophilic in character, allowing the silver halide crystals to ripen, dividing the resulting aqueous dispersion into portions, and admixing a dilferent polyvinyl acetal color former capable of forming upon color coupling development of an exposed silver salt image a dye taken from the group consisting of quinoneimine and azomethine dyes and containing in one of its tautomeric forms as an integral part of the molecule an active coupling group of the structure where X is taken-from the group consisting of primary amino, secondary amino and OH groups and n is a munber taken from the group consisting of 0 and 1 with each of more than one of such portions. r

5. A process which comprises precipitating light-sensitive silver halides in an aqueous solution of a non-colorforming polyvinyl acetal taken fromthe group consisting of simple polyvinyl acetals of polyvinyl alcohol with benzaldehyde and mixed acetals of polyvinyl alcohol with benzaldehyde and an aldehyde taken from the class consisting of aliphatic and aromatic carboxylic and sulfonic acids and their Water-soluble salts, the carboxylic and sulfonic groups being the sole substituent groups attached to the hydrocarbon nucleus of said aldehydes, said poly 10 a 1 vinyl acetals containing a large number of recurring intralinear -CH --CHOH- groups and being hydrophilic in character, allowing the silver halide crystals to ripen, removing the Water-soluble salts, dividing the resulting aqueous dispersion into portions, and admixing a differpolyvinyl acetal color former capable of forming upon color coupling development of an exposed silver salt image a dye taken from the group consisting of quinoneimine and azomethine dyes and containing in one of its tautomeric forms as an integral part of the molecule an active coupling group of the structure where X is taken from the group consisting of primary amino, secondary amino and OH groups and n is a number taken from the group consisting of 0 and 1 with each of more than one of such portions.

6. A process which comprises precipitating light-sensitive silver halides in an aqueous solution of a non-colorforming polyvinyl acetal taken from the group consisting of simple polyvinyl acetals of polyvinyl alcohol with benzaldehyde and mixed acetals of polyvinyl alcohol with benzaldehyde and an aldehyde taken from the class consisting of aliphatic and aromatic carboxylic and sulfonic acids and their water-soluble salts, the carboxylic and sulfonic groups being the sole substituent groups attached to the hydrocarbon nucleus of said aldehydes, said polyvinyl acetals containing a large number of recurring intralinear CH CHOH- groups and being hydrophilic in character, allowing the silver halide crystals to ripen, dividing the resulting aqueous dispersion into portions, admixing a different polyvinyl acetal colloid color former capable of forming upon color coupling development of an exposed silver salt image a dye taken from the group consisting of quinoneimine and azomethine dyes and containing in one of its tautomeric forms as an integral part of the molecule an active coupling group of the structure where X is taken from the group consisting of primary amino, secondary amino and OH groups and n is a number taken from the group consisting of O and l with each of more than one of such portions, and separately coating the portions as layers on a sheet support.

7. A process which comprises precipitating light-sensitive silver halides in an aqueous solution .of a non-colorforming polyvinyl acetal taken from the group consisting of simple polyvinyl acetals of polyvinyl alcohol with benzaldehyde and mixed acetals of polyvinyl alcohol with benzaldehyde and an aldehyde taken from the class consisting of aliphatic and aromatic carboxylic and sulfonic acids and their water-soluble salts, the carboxylic and sulfonic groups being the sole substituent groups attached to the hydrocarbon nucleus of said aldehydes, said polyvinyl acetals containing a large number of recurring intralinear CH CHOH groups and being hydrophilic in character, allowing the silver halide crystals to ripen, removing the water-soluble salts, dividing the resulting aqueous dispersion into portions, admixing a different polyvinyl acetal colloid color former capable of forming upon color coupling development of an exposed silver salt image a dye taken from the group consisting of quinoneimine and azomethine dyes and containing in one of its tautomeric forms as an integral part of the molecule an active coupling group of the structure where X is taken from the group consisting of primary amino, secondary amino and OH groups and n is a number taken from the group consisting of 0 and l with each of more than one of such portions, and separately coating the portions as layers on a sheet support.

8. A process which comprises precipitating a mixture a 1 l of light-sensitive silver halides in an aqueous solution of a non-color-forming polyvinyl acetal taken from the group consisting of simple polyvinyl acetals of polyvinyl alcohol with benzaldehyde and mixed acetals of polyvinyl alcohol With benzaldehyde and an aldehyde taken from the class consisting of aliphatic and aromatic carboxylic and sulfonic acids and their water-soluble salts, the carboxylic and sulfonic groups being the sole substituent groups attached to the hydrocarbon nucleous of said aldehydes, said polyvinyl acetals containing a large number of recurring intralinear -CH CHOH- groups and being hydrophilic in character, allowing the silver halide crystals to ripen, removing the water-soluble salts, dividing the resulting aqueous dispersion into portions, admixing a different hydrophilic polyvinyl acetal colloid color former capable of forming upon color coupling development of an exposed silver salt image a dye taken from the group consisting of quinoneimine and azomethine dyes and containing in one of its tautomeric forms as an integral part of the molecule an active coupling group of the structure Where X is taken from the group consisting of primary amino, secondary amino and OH groups and n is a number taken from the group consisting of 0 and 1 with each of three. of said portions, adding a dilferent spectral photographic sensitizing dye to each of two of such portions, and separately coating the portions as layers on a sheet support.

9. A process as set forth in claim 8 wherein the polyvinyl acetal color formers are respectively'capable of forming a dye taken from the group consisting of quinoneimine and azomethine dyes and each color former contains in one of its tautomeric forms as an integral part of the molecule an active coupling group of the structure where X is taken from the group consisting of primary amino, secondary amino and OH groups and n is a'number takenifrom the group consisting of O and 1 and said layers are sensitive to light of three different primary color regions of the spectrum.

10. A process which comprises precipitating a mixture of light-sensitive silver halides in an aqueous solution of a non-color-forming polyvinyl acetal taken from the group 7 consisting of simple polyvinyl acetals of polyvinyl alcohol with benzaldehyde and mixed acetals of polyvinyl alcohol with benzaldehyde and an aldehyde taken from the class consisting of aliphatic and aromatic, carboxylic and sulfonic acids and their water-soluble salts, the carboxylic and sulfonic groups being the sole substituent groups attached to the hydrocarbon nucleus of said aldehydes, said polyvinyl acetals containing a large number of recurring intralinear CH -CHOH groups and being hydrophilic in character, allowing the silver halide crystals to ripen, dividing the resulting dispersion into portions, ad'- mixing an aqueous solution containing a yellow polyvinyl acetal color former with one portion, a magenta polyvinyl acetal color former with another portion and a cyan polyvinyl acetal color former with a third portion, each of said color formers being capable of forming upon color coupling development of an exposed silver salt image a dye taken from the group consisting of quinoneimine and az-omethine dyes and containing in one of its tautomeric forms as an integral part of the molecule an active cou-.

pling group of the structure xr i=r i),.-t i=pn which confers green sensitivity to another of such emul-t sions and coating such emulsions as superposed layers on a support with a yellow light absorbing stratum disposed between the blue-sensitive silver halide emulsion layer and the red and green-sensitive layers. t V

ll. A process as set forth in claim 10 wherein each of said polyvinyl acetal color-formers is a mixed acetalhaving hydrophilic properties and contains acetal groups from sodium benzaldehyde o-sulfona'te.

12. A photographic composition comprising an admixture of a dispersion of'light-sen'sitive silver salts ma noncoloring-forming polyvinyl acetal taken front the group consisting of simple polyvinyl acetals of polyvinyl alcohol with benzaldehyde and mixed acetals of polyvinyl alcohol with benzaldehyde and an aldehyde taken from the class consisting of aliphatic and aromatic carboxylic and sulfonic acids and their water-soluble salts, the carboxylic and sulfonic groups being the sole substituent groups attached to the hydrocarbon nucleus of said aldehydes, said polyvinyl acetals containing a large number.

of recurring intralinear --CH CHOH-'- groups and being hydrophilic in character and a hydrophilic poly vinyl acetal color former capable of forming upon color coupling development of an exposed silver salt image a dye taken from the group consisting of quinoneimineand azomethine dyes and containing in one of its tautomeric, forms as an integral part of the molecule pling group of the structure where X is taken from the group consisting of primary amino, secondary amino and OH groups-and n is a number taken from the group consisting of 0 and l.

13. A composition as set forth in claim 1'2 wherein each of said polyvinyl acetal color-formers is a mixed acetal having hydrophilic properties and containing acetal groups from sodium benzaldehyde o-sulfonate each of' X((IJ=(IJ),.-(IJ=(IJH where X is taken from the group consisting of primary amino, secondary amino and OH groups and 'n is a number taken from the group consisting of O and 1*.

References Cited in the file of this patent UNITED STATES PATENTS 2,534,707 Glick et al. Dec. 19, I950 2,538,257 Martin Ian. 16, 1 95 1 2,599,494 Sloan June 3, 1952 2,606,835 Jennings a Aug. 1 2, 1952 an active-cou- 

7. A PROCESS WHICH COMPRISES PRECIPITATING LIGHT-SENSITIVE SILVER HALIDES IN AN AQUEOUS SOLUTION OF A NON-COLORFORMING POLYVINYL ACETAL TAKEN FROM THE GROUP CONSISTING OF SIMPLY POLYVINYL ACETALS OF POLYVINYL ALCOHOL WITH BENZALDEHYDE AND MIXED ACETALS OF POLYVINYL ALCOHOL WITH BENZALDEHYDE AND A ALDEHYDE TAKEN FROM THE CLASS CONSISTING OF ALIPHATIC AND AROMATIC CARBOXYLIC AND SULFONIC ACIDS AND THIER WATER-SOLUBLE SALTS, THE CARBOXYLIC AND SULFONIC GROUPS BEING THE SOLE SUBSTITUENT GROUPS ATTACHED TO THE HYDROCARBON NUCLEUS OF SAID ALDEHYDES, SAID POLYVINYL ACETALS CONTAINING A LARGE NUMBER OF RECURRING INTRALINEAR -CH2-CHOH- GROUPS AND BEING HYDROPHILIC IN CHARACTER, ALLOWING THE SILVER HALIDE CRYSTALS TO RIPEN, REMOVING THE WATER-SOLUBLE SALTS, DIVIDING THE RESULTING AQUEOUS DISPERSION INTO PORTIONS, ADMIXING A DIFFERENT POLYVINYL ACETAL COLLOID COLOR FORMER CAPABLE OF FORMING UPON COLOR COUPLING DEVELOPMENT OF AN EXPOSED SILVER SALT IMAGE A DYE TAKEN FROM THE GROUP CONSISTING OF QUINONEIMINE AND AZOMETHINE DYES AND CONTAINING IN ONE OF AN ACTIVE COUPLING GROUP OF THE STRUCTURE 